JPS6330215B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to bottle assemblies in which a polyethylene bottom lid is joined to a blow molded polyethylene terephthalate (PET) bottle by a novel hot melt adhesive composition. More particularly, the present invention relates to novel hot melt adhesive compositions having improved properties that are particularly useful in joining and assembling bottoms to PET bottles. BRIEF DESCRIPTION OF THE PRIOR ART Polyester bottles are widely used in the soft drink industry. These bottles are usually blow-molded, round-bottomed bottles that require a separate bottom lid to stand up straight. The bottom lid serves to keep the bottle sufficiently intact to withstand bottling, handling and storage conditions. The bottom lid is usually made of high-density polyethylene (HDPE) and is bonded to the bottle with hot melt adhesive. The forces that assembled bottles are subjected to during bottling, handling, and storage place the adhesive bond holding the bottom lid to the bottle under significant stress, which can cause the bottom lid and assembled bottle to peel or separate. Cause. Such stresses can cause empty bottles to delaminate before filling, so such bottles cannot be used in automatic filling lines. Once the bottle is filled, the pressure from the contents improves the mechanical fit between the bottle and the lid, causing the lid to remain attached to the bottle. However, once any part of the contents is lost, this improved fit is lost and the adhesive must prevent the bottle and lid from coming apart. The adhesive must also withstand the stresses to which the assembled bottle is subjected before and after filling due to varying temperature and humidity conditions. The soft drink filling industry has developed a series of standards that assembled bottles must meet. For example, an assembled bottle is cooled to -17.8°C (0〓) when empty and 4.5°C (40〓) when dropped from a height of 1.83 m (6 feet) and filled.
Do not let go when dropped from a height of 1.83 meters. Taylor et al. disclose in U.S. Pat. No. 4,212,910 (corresponding to Japanese Patent Application Laid-open No. 154,235/1983) that the adhesive composition is a styrene-butadiene-styrene type or styrene-isoprene-styrene type block copolymer, A prefabricated bottle is described and claimed which is a mixture of a tackifying resin, a stabilizer and a wax or oil diluent. Although this composition is an improvement over previously used adhesives, it is not without drawbacks. For example, the bond strength of the adhesive composition at room temperature is lower than required, and the temperature stability of the composition leaves room for improvement. SUMMARY OF THE INVENTION It is a general object of the present invention to ensure that the adhesive bond between the PET bottle and the bottom lid withstands all the normal stresses that the assembled bottle would be subjected to.
The purpose is to manufacture PET prefabricated bottles. Yet another object of the present invention is to provide an adhesive composition that, when used in PET prefabricated bottles, produces an adhesive bond that meets the standards required by the bottling industry. The adhesive composition used in the present invention is selected from the following (1).
It is a mixture of the components of (5): (1) A-B-A type block copolymer in which A is a monovinyl aromatic hydrocarbon and B is a conjugated diene or a rubber monoolefin.
(a) and a teleblock copolymer (b) consisting of a molecule having at least three branches radially branching from a central segment, each branch having a polystyrene terminal block and a butadiene central segment; (2)
an ethylene-vinyl acetate copolymer; (3) at least one tackifying resin that serves to increase the adhesion of the mixture system; (4) at least one stabilizer; and (5)
At least one type of wax or oil-based diluent. The adhesive composition used in the present invention contains an ethylene-vinyl acetate copolymer as one of its basic components, as disclosed in the US patent of Taylor et al.
It is significantly different from the adhesive composition of No. 4212910. The inventors have discovered that the addition of an ethylene-vinyl acetate copolymer to the adhesive composition described in the Taylor et al. patent provides all the advantages of the Taylor et al. has been improved,
They also discovered that the stability at high temperatures is improved. The discovery that the addition of ethylene-vinyl acetate copolymers provides such benefits is surprising. This is because the patent specification of Taylor et al. states that the use of known hot melt adhesives based on ethylene-vinyl acetate copolymer (EVA) cannot meet the standards of the bottling industry in the case of PET prefabricated bottles. (Column 1, lines 52-56 and column 6, lines 6-32 of the patent specification). The patent specifications of Taylor et al.
It is clear that there is no suggestion to those skilled in the art that the addition of ethylene-vinyl acetate copolymer to the Taylor et al. adhesive compositions would result in any improvement in these compositions. Assembled bottles made using the adhesive composition of the present invention have a bond that combines excellent adhesion and flexibility at low, normal and high temperatures, as well as high bond strength. DESCRIPTION OF THE PREFERRED EMBODIMENTS The block copolymer component (1) of the hot melt adhesive used in the present invention may be one of two specific sets: (a) Each monomer part is arranged alternately so as to have a general structure of A-B-A, where A is an inelastic block consisting of a monovinyl aromatic hydrocarbon monomer part, and B is an elastomeric polymer block consisting of either a conjugated diene monomer or a mono-olefin, such that the total concentration of the A block is in the range of about 10-50% of the total weight of the polymer. Sulfur elastic block polymer. Among these polymers, styrene is commonly used as the monovinyl aromatic hydrocarbon monomer.
The most commonly used conjugated diene monomers are butadiene-1,3 and isoprene. Thus, for example, styrene-butadiene-styrene polymers are available from Shell Chemical Co. as "Kraton 1101" and "Kraton 1102."
1101, -1102).
In addition, styrene-isoprene-styrene polymers are "Kraton 1107" and "Kraton 84-0554".
It is sold under the trademark . Although ethylene butylene monomer is commonly used as the monoolefin, other monomer components may also be used. A styrene-ethylenebutylene-styrene copolymer suitable for use is commercially available from Schiel Chemical Company under the trademark "Krayton G". A preferred block copolymer for use in the compositions of this invention is Kraton 1102. (b) A teleblock copolymer having at least three branches radially branching from a central segment, each branch comprising a molecule having a polystyrene terminal block and a butadiene central segment.
This type of block copolymer may also be referred to as a branched, polymerized butadiene center block with a polystyrene end block at the end of each branch. In all cases the number of butadiene units must be greater than the number of styrene units. A typical teleblock copolymer is trademarked as SOLPRENE and is manufactured by Phillips Petroleum Company.
Company). Mixtures of any of the above block copolymers can of course also be used as the base component of the adhesive used in the PET assembly bottles of the present invention. The ethylene-vinyl acetate copolymer component (2) of the hot melt adhesive used in the present invention is well known in the art, particularly as a resin for mixing in hot melt coatings and adhesives. Several manufacturers produce this copolymer.
Du Pont's Plastic Products and Resins Division manufactures a number of products with different combinations of composition and viscosity under the general trademark "Elvax". Elvax resin is sold in "grades" based on vinyl acetate content. For example, 200-series resins contain approximately 28 percent vinyl acetate, 300-series 25 percent, and 400-series 18 percent vinyl acetate.
Contains % vinyl acetate. Within each of these series, the higher the grade number, the higher the intrinsic viscosity. For example, the intrinsic viscosity of Elvax 210 is 0.54, Elvax 260 is 0.94, and Elvax 260 is 0.94.
265 is 1.01. Among these resins, Elvax 210 with a melt index of 400 is particularly effective when used in the composition of the present invention. All grades of Elvax are stabilized with the addition of 50-1000 ppm of butylated hydroxytoluene to prevent viscosity changes during use. It is believed that the tackifying resin (3) used in the hot melt adhesive of the present invention increases the adhesion of the block polymer. The term "tackifier resin" as used herein means the following resins (a) to (e). (a) natural and modified rosins such as rubber rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin and polymerized rosin; (b) glycerin ester of pale rosin, hydrogenated rosin; (c) ASTM
A polyterpene resin with a softening point of approximately 60 to 140°C as measured by method E2858T. These high softening point polyterpene resins are usually obtained by polymerizing terpene hydrocarbons, such as the bicyclic monoterpene known as pinene, in the presence of Friedel-Crafts catalysts at relatively low temperatures; (d) (e) a phenol-modified terpene resin, such as a resin product obtained by condensing a bicyclic terpene and a phenol in an acidic medium; and (e) a ring and ball softening point of about 60 to 140°C.
Aliphatic petroleum-based hydrocarbon resins, among which resins with high softening points, are obtained by polymerization of monomers mainly consisting of olefins and diolefins. Particularly recommended is Sylvachem Corporation of Jacksonville.
It is a polymerized tall oil rosin sold under the name SYLVATAC95 from Jacksonville, Florida, Florida. The stabilizer (4) used in the hot melt adhesive compositions of the present invention, in some sense, stabilizes the susceptible block polymer and thus the entire adhesive system during the manufacture and use of the adhesive and further stabilizes the final bond. Helps protect against thermal and oxidative degradation commonly encountered in conditions to which the product is normally exposed. Ethylene-vinyl acetate copolymers are also believed to help protect the block polymer from thermal and oxidative degradation. Such degradation is usually manifested in a deterioration in appearance, physical properties, and practical performance. Stabilizers used include polyfunctional phenols such as high molecular weight sterically strained phenols and phenols containing sulfur and phosphorus. Hindered phenols are well known to those skilled in the art and are phenolic compounds characterized by having a sterically bulky group in the immediate vicinity of their phenolic hydroxyl group. In particular, at least one of the ortho positions of the phenolic hydroxyl group usually contains a tert-butyl group as a substituent. When such a sterically bulky substituent exists near a hydroxyl group, its stretching vibration and therefore its reactivity are suppressed. This steric hindrance thus provides a phenolic compound with stabilizing properties. Representative hindered phenols are 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythrityltetrakis-3(3,5-di tert-butyl-4-hydroxyphenyl) propionate,
n-octadecyl-3(3,5-di-tert-butyl-
4-hydroxyphenyl)propionate; 4,
4'-methylene-bis(2,6-di-tert-butylphenol);2,2'-methylenebis(4-methyl-
6-tert-butylphenol);4,4'-thiobis(6-tert-butyl-o-cresol);2,6-di-tert-butylphenol); 6-(4-hydroxyphenoxy)-2, 4-bis(n-octylthio)-
1,3,5-triazine; 2,4,6-tris(4-hydroxy-3,5-di-tert-butylphenoxy)-1,3,5-triazine; di-n-octadecyl-3,5-di- tert-butyl-4-hydroxybenzylphosphonate; 2-(n-octylthio)ethyl-3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa[3-(3,5-di-tert-butyl-4 -hydroxyphenyl)propionate]. A particularly recommended stabilizer is Tris (monophenyl phosphate), commercially available from Weston under the trade name TNPP. The performance of these stabilizers is further enhanced when combined with (1) and (2): (1) synergists, such as thiodipropionates and phosphites, and (2) acetic acid,
its salts, and chelating agents and metal deactivators such as disalicilal propylene diimine. Wax or oil-based diluent used in the present invention
(5) reduces the melt viscosity or cohesiveness of a hot melt adhesive composition without appreciably degrading its adhesive bonding properties. The wax-based diluent used includes the following: (1) Hardness measured by ASTM method D-1321 is about 0.1 to
120, the ASTM softening point is approximately 65.6~121℃ (150~
250〓) with a low molecular weight, for example 1000 ~
6000 polyethylene, (2) melting point about 54.5-79.5℃
(130~175〓) paraffin wax and ASTM
Melting point measured by method D127-60 is approximately 57.2-93.3℃
(135-200〓); (3) atactic polypropylene with a ring and ball softening point of approximately 120-160°C; and (4) Fischer-Tropsch wax. A synthetic wax made by polymerizing carbon monoxide and hydrogen. All of these wax-based diluents are solid at room temperature. Hydrogenated animal, fish, and vegetable oils such as hydrogenated tallow, pork oil, soybean oil, cottonseed oil, castor oil, menhedeine oil, and cod liver oil are solid at room temperature due to hydrogenation, so they cannot be used as wax-based diluents. It turned out to be useful as an equivalent item. These hydrides are often referred to in the adhesive industry as "animal or vegetable waxes." Additionally, hydrocarbon oils, especially naphthenic or paraffinic process oils, are also used as diluents in the present invention. In particular, paraffin wax with a melting point of 150℃ and white mineral oil
It is best to use it together with oil) USP. The novel hot melt adhesive composition of the present invention typically includes a block polymer at a concentration of about 20-40%, an ethylene-vinyl acetate copolymer at a concentration of about 5-20%, and a tackifier at a concentration of about 30-60%. Resin, concentration approximately 0.1-4%
stabilizers and a wax or oil concentration of about 10-30%. These concentrations are values calculated based on the total solid weight of the hot melt adhesive composition as 100%. The hot melt adhesive compositions used in the present invention are formulated using any technique known in the art. Typical methods are as follows:
A mixing device with a jacket, preferably of the Baker-Perkins type with an agitator.
Pour about half of the tackifying resin, all of the wax, oil, and stabilizer into a heavy-duty Perkins or Day-type mixer with a jacket, and immediately bring the temperature to about 121-176.7°C (250-350°C). ), preferably 149
Raise to ℃ (300〓). The exact temperature used will depend on the melting points of the particular ingredients. Once the starting mixture is melted and mixed, CO ₂ is slowly bubbled through the mixture to cover the mixture before the block polymer is added. After this block polymer is dissolved, the ethylene-vinyl acetate copolymer is added and mixed until smooth.
Then add the remaining tackifying resin and continue mixing until well mixed. The viscosity of the hot melt composition is 162.8°C (325°C).
〓) is preferably about 4000 centipoise. Optional additives may be added to improve the properties of the hot melt composition. These additives include pigments such as titanium oxide and fillers such as talc and clay. The PET assembled bottle of the present invention is usually produced by feeding the bottle and the bottom lid onto a linear or centrifugal feeder, and applying hot melt adhesive in the form of small droplets from a multi-hole nozzle to a coating amount of about 0.4 to 0.75 g per bottom lid. The bottle and bottom lid are then squeezed together for at least 6.5 seconds to ensure that the droplets of hot melt adhesive are connected into a line and properly set. The assembled bottles are then labeled, packaged, and placed on pallets for shipping for bottling operations. The embodiments of the present invention will be explained in more detail with reference to the following reference examples and examples. Reference example: A sturdy pot-shaped mixer equipped with paddle-shaped stirring blades is heated to 149℃ (300℃), and the melting point is 65.6℃.
(150〓) Paraffin Wax 373.8 Kg (824 lb), White Mineral Oil USP 249 Kg (549 lb), Tris Monophenol Phosphate (Weston
TNPP) (Weston TMPP) 3.6Kg ((8 pounds)
and polymerized tall oil rosin (Silbatac 95
(Sylvatac95) 488.5Kg (1077lb) was loaded. The mixture was melted, mixed, and slowly charged with carbon dioxide, followed by the addition of 622.8 kg (1373 lbs.) of a block polymer available from Shell Chemical Company under the trademark "Kraton 1102."
After the block polymer had melted, 249 kg (549 lb) of ethylene-vinyl acetate copolymer (Elvax 210) having a melt index of 400 was added with stirring. After this mixture is smooth, polymerized tall oil rosin (Silbatac 95) 508Kg
(1120 lbs.) was added. When stirring is slowed down,
Continue mixing until you have a homogeneous, well-mixed mass. The molten mixture is poured into a partitioned container and allowed to solidify. The product thus obtained has a melt viscosity of 162.8 °C (325
〓) was about 4000 centipoise. Example Using the hot melt adhesive composition prepared in the reference example above, a PET prefabricated bottle was manufactured using conventional manufacturing equipment. This assembled bottle was tested using various test methods established by the bottling industry and was shown to meet or exceed these standards. For comparison, similar tests were conducted using the composition of the present invention and an adhesive composition that was identical to the composition of the present invention except that it did not contain the ethylene-vinyl acetate copolymer. The test results are shown in the table below.

【table】

【table】

[Table] From the above test results, it is clear that the adhesive containing ethylene-vinyl acetate copolymer used in the present invention has excellent high-temperature stability. The prefabricated bottle of the present invention is highly resistant to adhesive peeling and separation of the bottom lid under stress at low to high temperatures. I understand. It will be apparent to those skilled in the art that the above examples are illustrative and that the proportions, methods and materials may be varied without departing from the scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

Claims (1)

[Claims] 1. A blow-molded polyethylene terephthalate (PET) bottle and a high-density polyethylene bottom lid,
is a monovinyl aromatic hydrocarbon, B is either a conjugated diene or a rubber monoolefin, and at least three copolymers branched radially from the central segment. A type of block copolymer (1) selected from the group consisting of teleblock copolymers (b) consisting of a molecule having branches, each branch having a terminal block of polystyrene and a central segment of butadiene, ethylene-
A hot melt adhesive consisting of a mixture of a vinyl acetate copolymer (2), a tackifying resin (3) that serves to increase the adhesion of the system, a stabilizer (4), and a wax or oil-based diluent (5). A polyethylene terephthalate (PET) assembled bottle characterized by being made by combining them. 2. The block copolymer is a styrene-butadiene-styrene block copolymer, and the ethylene-vinyl acetate copolymer has a melt index of about 400 and contains about 28% vinyl acetate. The polyethylene terephthalate (PET) assembled bottle described in paragraph 1. 3 Wax-based diluent has a hardness of 0.1 to 120, ASTM
Low molecular weight polyethylene with a softening point of 65.6~121℃ (150~250〓), a melting point of 54.5~79.5℃ (130~175〓)
〓) Petroleum-based wax, melting point 57.2-93.3℃ (135
Microcrystalline waxes of ~200㎓), atactic polypropylenes with a ring and ball softening point of 120-160°C, synthetic waxes made by polymerization of carbon monoxide and hydrogen, and hydrogenated animals, fish and plants. Claim 1 selected from the group consisting of oils and fats.
Polyethylene terephthalate (PET) as described in
Assembled bottle. 4. The polyethylene terephthalate (PET) prefabricated bottle according to claim 1, wherein the oil-based diluent is mineral oil. 5 The block copolymer is styrene-isoprene-
A polyethylene terephthalate (PET) assembly bottle according to claim 1, which is a styrene-block copolymer. 6 Tackifying resins include natural and modified rosins, glycerin and pentaerythritol esters of natural and modified rosins, polyterpene resins with a softening point of 60 to 140°C, phenol-modified terpene resins, and aliphatic resins with a ring and ball softening point of 60 to 140°C. A polyethylene terephthalate (PET) prefabricated bottle according to claim 1 selected from the group consisting of petroleum-based hydrocarbon resins. 7. The polyethylene terephthalate (PET) assembled bottle according to claim 1, wherein the stabilizer is a sterically hindered phenol or a polyfunctional phenol with a large molecular weight. 8 The total solids weight of a hot melt adhesive is
When taken as 100%, about 20 to 40% block polymer,
Approximately 5-20% ethylene-vinyl acetate copolymer, approx.
A polyethylene terephthalate (PET) prefabricated bottle according to claim 1, comprising 30-60% tackifying resin, about 0.1-4% stabilizer and 10-30% wax or oil diluent.